This invention relates generally to the formation of loosely compacted fiber mats and, more particularly, to a machine for improving the uniformity of the mat as it is continuously formed.
Fibrous mats have been formed from compact fiber sheets on known machines for many years. One known procedure and machine comprises a device such as a pin-mill which has a rotor with a substantial number of sharp pins mounted about the periphery and enclosed by an outer shell. Incoming compacted fiber sheets, such as pulp sheets, are caused to impinge upon the passing pins, whereby the compacted fiber sheet is converted into individual fibers or small clumps of fibers and is then substantially in an air-fiber mixture within the annular volume between the pins and the shell. The air-fiber mixture is then directed through a conduit exiting from the shell to a typical mat-laying station, which may be comprised of an endless foraminous screen with a suction box beneath the screen. The fibers remain on the foraminous screen and will form a loosely compacted mat of fibers. One such use of a typical fiberizing and mat-layig machine is to convert incoming pulp sheets to a continuous fluff mat, which would then be suitable for cutting into desired lengths for use in diapers. A typical commercially available machine suitable for fiberizing pulp sheets and for laying down a loosely compacted mat is one available from Curt G. Joa, Inc. of Sheboygan Falls, Wisc. These known machines are capable of fiberizing a plurality of incoming compacted fiber sheets with the number varying dependent upon the thickness, width and density of the loosely compacted mat to be formed.
One of the problems in known machines is that when incoming compacted fiber sheets have widths that are greater than the loosely compacted mat width to be formed, the fiberizing process together with use of a converging duct tends to result in a nonuniform mat density and/or one which is very uneven requiring a typical scalping spinner or comb for leveling. Typically, scalping degrades some of the fiber and reduces the interlocking bonds of much of the fiber. Clumps of fibers are sometimes displaced, resulting in holes or thin areas within the mat. As will be recognized by those skilled in the art, holes or thin areas can degrade the mat to such an extent that certain sections become unusable and therefore result in a significant amount of waste and/or additional processing time to cut out the unacceptable portion of the mat. The known machines simply provide converging ducts leading from the fiberizer housing and it has been found that simple converging ducts do not provide the uniformity required to result in continuously produced uniform mat properties.
Accordingly, from the foregoing, one object of the present invention is to provide an air-fiber mixture that will result in a continuously formed mat having uniform thickness and density over the desired width.
Another object of the present invention is to provide a fiberizing machine capable of generating air-fiber mixtureshaving variable widths while maintaining the uniform density across the width and thereby within the formed mat.
A further object of this invention is to provide a machine that is of simple construction, high reliability and simple in operation.
Yet another object of this invention is to provide an improvement that may be incorporated within existing fiberizing machines and at low cost.
These and other objects will become more apparent and better understood upon reading the specification to follow in conjunction with the attached drawings.